Lager yeast is referred to as bottom fermenting yeast. Compared to ale yeast they generally don’t foam as much at the surface and tend to fall to the bottom of the fermenter as fermentation nears completion. The main difference between ale yeast and lager yeast is the fermentation temperature. Ale yeast perform best in the range of 62 – 72°F where lager strains prefer much cooler temperatures in the 50 – 55°F range. Lager yeast also grow much more slowly then ale yeast making it necessary to pitch lager amounts of cells then ale yeast, especially at cooler pitching temperatures. Some recommend pitching the yeast at warmer temperatures and gradually lowering the fermentation temperature to the 50 - 55°F range to promote yeast growth. Most professionals would disagree pointing out that most flavor development happens in the first 24 hours of fermentations so avoiding warmer temperatures in the early stages help eliminate ester development. Either way, White Labs provides you with quality strains of lager yeast to produce the best beer possible.